WordPress – How to change Visual Composer Read More button text
Go to wp-content\plugins\js_composer\include\params\vc_grid_item\templates.php
Find following piece (might be more of them in separate lines)
__( 'Read More', 'js_composer' )
Replace Read More text with your text. Repeat this for other lines where you see same line of code in this file.
My recommendation is to use Replace feature of Notepad++.